The invention relates to aliphatic polycarbonate homo- and co-polymers which are obtained by ring-opening homo- or co-polymerization of cyclic carbonates by DMC catalysis.
Double metal cyanide (DMC) catalysts useful for the ring-opening polymerization of oxygen-containing, cyclic monomers have been known for a long time. DMC catalysts are of particular commercial interest for the production of polyether polyols by polyaddition of epoxides to starter compounds exhibiting active hydrogen atoms (See, e.g., U.S. Pat. Nos. 3,404,109; 3,829,505; 3,941,849 and 5,158,922.) because the use of a DMC catalyst reduces the proportion of monofunctional polyethers with terminal double bonds (so-called xe2x80x9cmono-olsxe2x80x9d) compared to polyether polyols produced using conventional alkaline catalysts. Moreover, improved, highly active DMC catalysts, which are described, e.g., in U.S. Pat. No. 5,470,813; EP-A 700 949; EP-A743 093; EP-A 761 708; WO 97/40086; WO 98/16310 and WO 00/47649, possess extraordinarily high activity and permit polyether polyol production at very low catalyst concentrations (25 ppm or less). Consequently, it is no longer necessary to separate the catalyst from the finished product. In addition, DMC catalysts also make possible the homo- and co-polymerization of other oxygen-containing, cyclic monomers, such as oxetanes, (U.S. Pat. Nos. 3,278,457 and 3,404,109), cyclic anhydrides (U.S. Pat. Nos. 5,145,883 and 3,538,043) and lactones (U.S. Pat. No. 5,032,671).
Aliphatic polycarbonate homo- and co-polymers are suitable as additives for thermoplastic systems. Moreover, aliphatic, OH-functional polycarbonates are widely used as a hydroxyl component for building up polyurethanes and polyurethane-urea elastomers. Common methods for the production of aliphatic polycarbonates are transesterification of a diol with a dialkyl carbonate from a short-chain alcohol, with a dioxolanone or with a diphenyl carbonate. These reactions are accelerated by catalysts, particularly alkali, tin and titanium compounds (See, e.g., Kunststoffhandbuch, vol. 3/1 Polycarbonate, Hanser Verlag, Munich, 1992, p. 118f.).
It has now been found that aliphatic polycarbonate homo- and co-polymers can be obtained by ring-opening homo- or co-polymerization of a cyclic carbonate by DMC catalysis.
The present invention relates to aliphatic polycarbonate homo- and co-polymers, which are obtained entirely or partly by ring-opening homo- or co-polymerization of cyclic carbonates by DMC catalysis.
Suitable cyclic carbonates useful in the practice of the present invention may be represented by the general formula (I.) or (II.) 
in which
m, n, p and q, independently of one another, each represents 0, 1, 2, 3, 4, or 6 and
R1 and R2 represent H, a C1-6 alkyl, a C3-6 alkenyl, or a C16 alk(en)yloxy-C1-6 alkyl group, particularly H, CH3 and C2H5.
Preferred cyclic carbonates represented by formula (I) or (II) include: trimethylene glycol carbonate, neopentyl glycol carbonate, 1,4-butanediol carbonate and dimeric carbonates of pentanediol or of hexanediol. Particularly preferred are 6-membered ring carbonates, particularly neopentyl glycol carbonate.
Suitable DMC catalysts are known and are described in detail in the disclosures discussed in the Background of the Invention. Improved, highly active DMC catalysts, such as those described in U.S. Pat. No. 5,470,813; EP-A 700 949; EP-A 743 093; EP-A 761 708; WO 97/40086; WO 98/16310 and WO 00/47649, are preferably used. The highly active DMC catalysts described in EP-A 700 949, which, in addition to a double metal cyanide compound (e.g. zinc hexacyano-cobaltate(III)) and an organic complex ligand (e.g. tert.-butanol), also contain a polyether with a number-average molecular weight of more than 500 g/mole, are typical examples of suitable catalysts.
The DMC-catalyzed, ring-opening homo- or co-polymerization of the cyclic carbonate generally takes place at temperatures of from 20 to 200xc2x0 C., preferably in the range of from 40 to 180xc2x0 C., most preferably at temperatures of from 80 to 160xc2x0 C. The reaction can be conducted under a total pressure of from 0.001 to 20 bar. The polymerization can be performed in substance or in an inert, organic solvent, such as toluene or tetrohydrofuran (THF). If used, the quantity of solvent is generally from 10 to 30 wt. %, based on the total amount of polymer to be produced.
The catalyst concentration is generally in the range of from 0.0005 wt. % to 1 wt. %, preferably in the range of from 0.001 wt. % to 0.1 wt. %, most preferably in the range of from 0.001 to 0.05 wt. %, based on the total amount of polymer to be produced.
The polymerization can be performed continuously or non-continuously, e.g. in a batch or semi-batch process.
The DMC-catalyzed, ring-opening homo- or co-polymerization of the cyclic carbonate is optionally performed in the presence of one or more starter compounds exhibiting active hydrogen atoms. In this way, OH-functionalized aliphatic polycarbonate homo- and co-polymers that are suitable as polyol components for building up polyurethane systems can be produced.
Compounds with molecular weights of from 18 to 10,000 g/mole and having from 1 to 8 hydroxyl groups are preferably used as starter compounds exhibiting active hydrogen atoms. Examples of such compounds include: water, ethanol, butanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butanediol, hexamethylene glycol, bisphenol A, trimethylolpropane, glycerol, pentaerythritol, sorbitol, cane sugar, degraded starch, polyether polyols and polyester polyols.
The DMC-catalyzed, ring-opening polymerization of the cyclic carbonate can be performed as a homo-polymerization, optionally in the presence of one or more starter compounds exhibiting active hydrogen atoms.
The DMC-catalyzed, ring-opening polymerization of the cyclic carbonates can also be performed as a co-polymerization, again optionally in the presence of one or more starter compounds exhibiting active hydrogen atoms. Both random co-polymerization and block co-polymerization are possible.
In random co-polymerization, the DMC-catalyzed, ring-opening polymerization of the cyclic carbonate is performed in the presence of one or more other monomers suitable for polymerization with a DMC catalyst. Particularly suitable for random co-polymerization with cyclic carbonates are: epoxides, particularly ethylene oxide, propylene oxide and butylene oxide and mixtures thereof; oxetanes; cyclic anhydrides, such as phthalic anhydride; cyclic esters, such as caprolactone; and lactides.
In the production of polycarbonate block co-polymers in accordance with the present invention, the aliphatic polycarbonate block is obtained by means of DMC-catalyzed, ring-opening polymerization of a cyclic carbonate. Preferred block co-polymers include: poly(ester-block-carbonate) co-polymers and poly(ether-block-carbonate) co-polymers, in which the ester or ether block can be obtained by any of the known processes or catalysts.
In a preferred embodiment of the process of the present invention, a polyether polyol is first produced by any of the known methods, e.g., by DMC-catalyzed polyaddition of an epoxide, (particularly propylene oxide and/or a propylene oxide/ethylene oxide mixture), to the starter compound exhibiting active hydrogen atoms (mentioned above). The polyether polyol containing the active DMC catalyst is then reacted with a cyclic carbonate in the manner according to the present invention, with ring-opening. In this reaction with the carbonate, secondary hydroxyl groups of the polyether polyol can be converted completely or partially into primary hydroxyl groups, which are more reactive with isocyanate groups. These poly(ether-carbonate) polyols are therefore of great interest for use in the production of polyurethanes.
Having thus described the invention, the following Examples are given as being illustrative thereof.